In the processing of substrates, for example, substrate etching processes, substrate deposition processes, and substrate and chamber cleaning processes, gases such as halogen or oxygen gases are used. The gases, especially when they are energized, for example by RF power or microwave energy, can corrode or erode (which terms are used interchangeably herein) components of the chamber, such as the chamber wall. For example, chamber components made of aluminum can be corroded by halogen gases to form AlCl3 or AlF3. The corroded components need to be replaced or cleaned off resulting in chamber downtime which is undesirable. Also, when the corroded portions of the components flake off and contaminate the substrate they reduce substrate yields. Thus, it is desirable to reducing corrosion of the chamber components.
The corrosion or erosion resistance of the aluminum chamber components may also be improved by forming an anodized aluminum oxide coating on the components. For example, an aluminum chamber wall may be anodized in an electroplating bath to form a protective coating of anodized aluminum oxide. The anodized coating increases the corrosion resistance of the aluminum chamber, but it still is sometimes degraded by highly energized or erosive gas compositions, for example, by an energized gas comprising a plasma of a fluorine containing gas, such as CF4, to form gaseous byproducts such as AlF3.
Conventional chamber components formed out of bulk ceramic materials or plasma sprayed ceramic coatings exhibit better erosion resistance but are susceptible to other failure modes. For example, chamber components formed out of a bulk material comprising a mixture of yttrium oxide and aluminum oxide, are brittle and tend to fracture when machined into a shape of a component. Bulk ceramic material may also be susceptible to cracking during operation of the chamber. Chamber components have also been made with plasma sprayed coatings. However, the thermal expansion mismatch between the coating and the underlying component material can cause thermal strains during heating or cooling that result in cracking or flaking off of the ceramic coating from the underlying component. Thus, conventional ceramic components do not always provide the desired corrosion and failure resistance.
For these and other reasons, further development of ceramic coatings and materials that provide improved corrosion or erosion resistance to corrosive energized gases is needed.